Images

GOODS-S field (NIRCam image)

Wed, 29 May 2024 10:00:00 +0200

How did the first stars and galaxies form? The NASA/ESA/CSA James Webb Space Telescope is already providing new insights into this question. One of the largest programs in Webb’s first year of science is the JWST Advanced Deep Extragalactic Survey, or JADES, which will devote about 32 days of telescope time to uncover and characterize faint, distant galaxies. While the data are still coming in, JADES already has discovered hundreds of galaxies that existed when the Universe was less than 600 million years old. The team also has identified galaxies sparkling with a multitude of young, hot stars.

This infrared image shows a portion of an area of the sky known as GOODS-South, which has been well studied by the NASA/ESA Hubble Space Telescope and other observatories. More than 45,000 galaxies are visible here.

Using these and other data, the JADES team has discovered hundreds of galaxies that existed when the Universe was less than 600 million years old. The sheer number of these galaxies was far beyond predictions from observations made before Webb’s launch. The team also has identified galaxies that existed during a time known as the Epoch of Reionization, when the Universe underwent a transformation from opaque to transparent. Many of these galaxies shown unusually strong emission line signatures due to the creation of multitudes of hot, massive stars.

In this image, blue, green, and red were assigned to Webb’s NIRCam (Near-Infrared Camera) data at 0.9, 1.15, and 1.5 microns; 2.0, 2.77, and 3.55 microns; and 3.56, 4.1, and 4.44 microns (F090W, F115W, and F150W; F200W, F277W, and F335M; and F356W, F410M, and F444W), respectively.

Star-studded cluster

Wed, 29 May 2024 10:00:00 +0200

This new image from the NASA/ESA/CSA James Webb Space Telescope features NGC 6440, a globular cluster that resides roughly 28 000 light-years from Earth in the constellation Sagittarius. The object was first discovered by William Herschel in May of 1786.

Globular clusters like NGC 6440 are roughly spherical, tightly packed, collections of old stars bound together by gravity. They can be found throughout galaxies, but often live on the outskirts. They hold hundreds of thousands to millions of stars that are on average about one light-year apart, but they can be as close together as the size of our Solar System. NGC 6440 is known to be a high-mass and metal-rich cluster that formed and is orbiting within the Galactic bulge, which is a dense, near-spherical region of old stars in the inner part of the Milky Way.

This image was obtained with 2023 data from Webb’s Near-InfraRed Camera (NIRCam) as part of an observation programme to explore the stars in the cluster and to investigate details of the cluster’s pulsars. A pulsar is a highly magnetised, rotating neutron star that emits a beam of electromagnetic radiation from their magnetic poles. To us, that beam appears as a short burst or pulse as the star rotates. Pulsars spin extremely fast. Astronomers have clocked the fastest pulsars at more than 716 rotations per second, but a pulsar could theoretically rotate as fast as 1500 rotations per second before slowly losing energy or breaking apart. The new data obtained by the science team indicate the first evidence from Webb observations of abundance variations of helium and oxygen in stars in a globular cluster. These results open the window for future, in-depth investigations of other clusters in the Galactic bulge, which were previously infeasible with other telescope facilities given the significant crowding of stars in the cluster and the strong reddening caused by interstellar dust between the cluster and Earth.

[Image Description: A spherical collection of stars which fills the whole view. The cluster is dominated by a concentrated group of bright white stars at the centre, with several large yellow stars scattered throughout the image. Many of the stars have visible diffraction spikes. The background is black.]

Preview image from MAST of one of the NIRSpec/MSA spectra of GN-z11

Wed, 29 May 2024 10:00:00 +0200

This image shows a preview from MAST of one of the NIRSpec/MSA spectra of GN-z11.

Conference group photo — Porto, Portugal

Wed, 29 May 2024 10:00:00 +0200

Conference participants from the ESA Hubble and Webb Science Conference held in Porto, Portugal from 29 April to 2 May 2024.

The lights of a galactic bar

Mon, 27 May 2024 06:00:00 +0200

This week, an image of the broad and sweeping spiral galaxy NGC 4731 is the Hubble Picture of the Week. This galaxy lies among the galaxies of the Virgo cluster, in the constellation Virgo, and is located 43 million light-years from Earth. This highly detailed image was created using six different filters. The abundance of colour illustrates the galaxy's billowing clouds of gas, dark dust bands, bright pink star-forming regions and, most obviously, the long, glowing bar with trailing arms.

Barred spiral galaxies outnumber both regular spirals and elliptical galaxies put together, numbering around 60% of all galaxies. The visible bar structure is a result of orbits of stars and gas in the galaxy lining up, forming a dense region that individual stars move in and out of over time. This is the same process that maintains a galaxy's spiral arms, but it is somewhat more mysterious for bars: spiral galaxies seem to form bars in their centres as they mature, accounting for the large number of bars we see today, but can also lose them later on as the accumulated mass along the bar grows unstable. The orbital patterns and the gravitational interactions within a galaxy that sustain the bar also transport matter and energy into it, fuelling star formation. Indeed, the observing programme studying NGC 4731 seeks to investigate this flow of matter in galaxies.

Beyond the bar, the spiral arms of NGC 4731 stretch out far past the confines of this close-in Hubble view. The galaxy’s elongated arms are thought to result from gravitational interactions with other, nearby galaxies in the Virgo cluster.

[Image Description: A close-in view of a barred spiral galaxy. The bright, glowing bar crosses the centre of the galaxy, with spiral arms curving away from its ends and continuing out of view. It’s surrounded by bright patches of light where stars are forming, as well as dark lines of dust. The galaxy’s clouds of gas spread out from the arms and bar, giving way to a dark background with some foreground stars and small, distant galaxies.]

A jewel in the queen’s hair

Mon, 20 May 2024 06:00:00 +0200

This Picture of the Week shows the jewel-bright spiral galaxy NGC 4689, which lies 54 million light-years from Earth in the constellation Coma Berenices. This constellation has the distinction of being the only one of the 88 constellations officially recognised by the International Astronomical Union (IAU) to be named after an historical figure, Queen Berenice II of Egypt. The latin word ‘coma’ references her hair, meaning that NGC 4689 can be said to be found in the hair of a queen. Some people of Berenice’s time would have meant this quite literally, as the story goes that her court astronomer thought that a missing lock of Berenice’s hair had been catasterised (a word meaning ‘placed amongst the stars’) by the gods: hence the name of the constellation, Coma Berenices.

NGC 4689 holds an interesting — albeit less royal — place in modern astronomy too. The Universe is so incredibly vast that at a distance of a mere 54 million light-years NGC 4689 is relatively nearby for a galaxy. This image has been made using data from two sets of observations, one made in 2019 and 2024, both of which were made as a part of programmes that observed multiple ‘nearby’ galaxies. The 2024 observing programme is an interesting example of how Hubble — a relatively old but extraordinarily productive telescope — can support the work of the technologically cutting-edge Webb telescope. Observations collected by Webb stand to transform our understanding of how galaxies transform and evolve over time, by providing data of an unprecedented level of detail and clarity. However, thanks to their complementary capabilities, new observations from Hubble — such as those used to create this image — can assist the work done using Webb. In this case, the Hubble data were collected in order to get a more accurate grasp of the stellar populations of nearby galaxies, which is crucial to understanding the evolution of galaxies. Thus, NGC 4689 is playing an important role in developing our understanding of how all galaxies evolve. In fact, it is observed enough that it has been the subject of a Hubble Picture of the Week before, in 2020.

[Image Description: A spiral galaxy is viewed close up and fills most of the scene. It has a bright, glowing spot at the core, broad spiral arms that are covered by many dark threads of dust, and pink glowing spots across the disc that mark areas of star formation. The disc of the galaxy is surrounded by a faint halo that bleeds into the dark background.]

Lenticular dust in detail

Mon, 13 May 2024 06:00:00 +0200

Featured in this new image from the NASA/ESA Hubble Space Telescope is a nearly edge-on view of the lenticular galaxy NGC 4753. These galaxies have an elliptical shape and ill-defined spiral arms.

This image is the object's sharpest view to date, showcasing Hubble’s incredible resolving power and ability to reveal complex dust structures. NGC 4753 resides around 60 million light-years from Earth in the constellation Virgo and was first discovered by the astronomer William Herschel in 1784. It is a member of the NGC 4753 Group of galaxies within the Virgo II Cloud, which comprises roughly 100 galaxies and galaxy clusters.

This galaxy is believed to be the result of a galactic merger with a nearby dwarf galaxy roughly 1.3 billion years ago. NGC 4753’s distinct dust lanes around its nucleus are believed to have been accreted from this merger event.

It is now believed that most of the mass in the galaxy lies in a slightly flattened spherical halo of dark matter. Dark matter is a form of matter that cannot currently be observed directly, but is thought to comprise about 85% of all matter in the Universe. It is referred to as ‘dark’ because it does not appear to interact with the electromagnetic field, and therefore does not seem to emit, reflect or refract light.

This object is also of scientific interest to test different theories of formation of lenticular galaxies, given its low-density environment and complex structure. Furthermore, this galaxy has been host to two known Type Ia supernovae. These types of supernovae are extremely important as they are all caused by exploding white dwarfs which have companion stars, and always peak at the same brightness — 5 billion times brighter than the Sun. Knowing the true brightness of these events, and comparing this with their apparent brightness, gives astronomers a unique chance to measure distances in the Universe.

[Image Description: Lenticular galaxy NGC 4753 is featured with a bright white core and surrounding defined dust lanes around its nucleus, that predominantly appear dark brown in colour. A variety of faint stars fill the background of the image.]

A star forming factory

Mon, 06 May 2024 06:00:00 +0200

The celestial object showcased in this week's Hubble Picture of the Week is the spiral galaxy UGC 9684, which lies around 240 million light-years from Earth in the constellation Boötes. This image shows an impressive example of several classic galactic features, including a clear bar in the galaxy's centre, and a halo surrounding its disc.

The impetus for this Hubble image was a study into the host galaxies of Type-II supernovae. These cataclysmic stellar explosions take place throughout the Universe, and are of great interest to astronomers, so automated surveys scan the night sky and attempt to catch sight of them. The supernova which brought UGC 9684 to Hubble's attention occurred during 2020. It has faded from view in this image, which was taken in 2023.

Remarkably, the 2020 supernova in this galaxy isn't the only one that's been seen there — four supernova-like events have been spotted in UGC 9684 since 2006, putting it up there with the most active supernova-producing galaxies. It turns out that UGC 9684 is a quite active star-forming galaxy, calculated as producing one solar mass worth of stars every few years! This level of stellar formation makes UGC 9684 a veritable supernova factory, and a galaxy to watch for astronomers hoping to examine these exceptional events.

[Image Description: A spiral galaxy in the centre of a dark background, surrounded by a few distant galaxies and nearby stars. The galaxy is tilted diagonally and partially towards the viewer. Its disc is cloudy and threaded with dust, without clear arms. A bar of light extends across the disc from the glowing core. A faint halo of gas surrounds the disc.]

On the hunt for X-rays

Mon, 29 Apr 2024 06:00:00 +0200

Featured in this Hubble Picture of the Week this week is the dwarf galaxy IC 776. This swirling collection of stars new and old is located in the constellation Virgo — in fact, in the Virgo galaxy cluster — 100 million light-years from Earth. While a dwarf galaxy, it's also been classified as an SAB-type or ‘weakly barred’ spiral, one study naming it a “complex case” in morphology. This highly detailed view from Hubble demonstrates that complexity well. IC 776 has a ragged, disturbed disc that nevertheless looks to spiral around the core, and arcs of star-forming regions.

This image is from an observation programme dedicated to the study of dwarf galaxies in the Virgo cluster, searching for sources of X-rays in such galaxies. X-rays are often emitted by accretion discs, where material that is drawn into a compact object by gravity crashes together and forms a hot, glowing disc. The compact object can be a white dwarf or neutron star in a binary pair, stealing material from its companion star, or it can be the supermassive black hole at the heart of a galaxy, devouring all around it. Dwarf galaxies like IC 776, travelling through the Virgo cluster, experience a pressure from the intergalactic gas which can both stimulate star formation and feed the central black hole in a galaxy. That can create energetic accretion discs, hot enough to emit X-rays.

While Hubble is not able to see X-rays, it can coordinate with X-ray telescopes such as NASA’s Chandra, revealing the sources of this radiation in high resolution using visible light. Dwarf galaxies are thought to be very important for our understanding of cosmology and the evolution of galaxies. As with many areas of astronomy, the ability to examine these galaxies across the electromagnetic spectrum is critical to their study.

[Image Description: A spiral galaxy viewed tilted at a diagonal angle. The core and the disc of the galaxy are different colours, but are otherwise difficult to tell apart, with the disc having wispy, ragged edges and many arcs of glowing star-forming patches. A few distant galaxies can be seen in the background around the spiral galaxy, as well as several foreground stars.]

Links

Pan video of IC 776

Little Dumbbell Nebula (M76, annotated)

Tue, 23 Apr 2024 16:00:00 +0200

In celebration of the 34th anniversary of the launch of the legendary NASA/ESA Hubble Space Telescope, astronomers took a snapshot of the Little Dumbbell Nebula (also known as Messier 76, M76, or NGC 650/651) located 3400 light-years away in the northern circumpolar constellation Perseus. The photogenic nebula is a favourite target of amateur astronomers.

M76 is classified as a planetary nebula. This is a misnomer because it is unrelated to planets. But its round shape suggested it was a planet to astronomers who first viewed it through low-power telescopes. In reality, a planetary nebula is an expanding shell of glowing gases that were ejected from a dying red giant star. The star eventually collapses to an ultra-dense, hot white dwarf.

M76 is composed of a ring, seen edge-on as the central bar structure, and two lobes on either opening of the ring. Before the star burned out, it ejected the ring of gas and dust. The ring was probably sculpted by the effects of the star that once had a binary companion star. This sloughed-off material created a thick disc of dust and gas along the plane of the companion’s orbit. The hypothetical companion star isn’t seen in the Hubble image, and so it could have been later swallowed by the central star. The disc would be forensic evidence for that stellar cannibalism.

The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known at a scorching 120 000 degrees Celsius, 24 times our Sun’s surface temperature.  The sizzling white dwarf can be seen as a pinpoint in the centre of the nebula. A star visible in projection beneath it is not part of the nebula.  

Pinched off by the disc, two lobes of hot gas are escaping from the top and bottom of the ‘belt’ along the star’s rotation axis that is perpendicular to the disc. They are being propelled by the hurricane-like outflow of material from the dying star, tearing across space at two million miles per hour. That’s fast enough to travel from Earth to the Moon in a little over seven minutes! This torrential ‘stellar wind’ is ploughing into cooler, slower-moving gas that was ejected at an earlier stage in the star’s life, when it was a red giant. Ferocious ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen. 

The entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15 000 years.

[Image description: Annotated image labeled “Little Dumbbell Nebula, M76, HST WFC3/UVIS” against the black background of space. Near top left, a color key consisting of five lines reads: “F475W SDSS g’” in light blue; “F502N OIII” in dark blue; “F656N Ha” in green; “F658N NIII” in red; and “F814W I” in orange. The nebula is located 3,400 light-years away in the northern circumpolar constellation Perseus. The name ‘Little Dumbbell’ comes from its shape that is a two-lobed structure of colorful, mottled, glowing gases resembling a balloon that’s been pinched around a middle waist. Like an inflating balloon, the lobes are expanding into space from a dying star seen as a white dot in the centre. Blistering ultraviolet radiation from the super-hot star is causing the gases to glow. The red color is from nitrogen, and blue is from oxygen. At bottom left corner is a scale bar labeled “1 light-year.” At bottom right corner, the “E” compass arrow points towards the 10 o’clock position. The “N” arrow points towards the 1 o’clock position.] 

Little Dumbbell Nebula (M76)

Tue, 23 Apr 2024 16:00:00 +0200

The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known at a scorching 120 000 degrees Celsius, 24 times our Sun’s surface temperature. The sizzling white dwarf can be seen as a pinpoint in the centre of the nebula. A star visible in projection beneath it is not part of the nebula.

The entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15 000 years.

[Image description: A Hubble image of the Little Dumbbell Nebula. The name comes from its shape, which is a two-lobed structure of colourful, mottled glowing gases that resemble a balloon that has been pinched around a middle waist. Like an inflating balloon, the lobes are expanding into space from a dying star seen as a white dot in the centre. Blistering ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.] 

Captured on glass

Mon, 22 Apr 2024 06:00:00 +0200

This Hubble Picture of the Week depicts the spiral galaxy ESO 422-41, which lies about 34 million light-years from Earth in the constellation Columba. The patchy, star-filled structure of the galaxy’s spiral arms and the glow from its dense core are laid out in intricate detail here by Hubble’s Advanced Camera for Surveys. Images of this galaxy have, however, a decades-long history.

The name ESO 422-41 comes from its identification in the European Southern Observatory (B) Atlas of the Southern Sky. In the times before automated sky surveys with space observatories such as ESA’s Gaia, many stars, galaxies and nebulae were discovered by means of large photographic surveys. Astronomers used the most advanced large telescopes of the time to produce hundreds of photographs, covering an area of the sky. They later studied the resulting photographs, attempting to catalogue all the new astronomical objects revealed.

In the 1970s a new telescope at ESO’s La Silla facility in Chile performed such a survey of the southern sky, which still had not been examined in as much depth as the sky in the north. At the time, the premier technology for recording images was glass plates treated with chemicals. The resulting collection of photographic plates became the ESO (B) Atlas of the Southern Sky. Astronomers at ESO and in Uppsala, Sweden collaborated to study the plates, recording hundreds of galaxies — ESO 422-41 being just one of those — star clusters, and nebulae. Many were new to astronomy.

Astronomical sky surveying has since transitioned through digital, computer-aided surveys such as the Sloan Digital Sky Survey and the Legacy Surveys, to surveys made by space telescopes including Gaia and the Wide-Field Infrared Survey Explorer. Even so, photographic sky surveys contributed immensely to astronomical knowledge for decades, and the archives of glass plates serve as an important historical reference for large swathes of the sky. Some are still actively used today, for instance to study variable stars through time. And the objects that these surveys revealed, including ESO 422-41, can now be studied in depth by telescopes such as Hubble.

[Image Description: A spiral galaxy, with a brightly shining core and two large arms. The arms are broad, faint overall and quite patchy, and feature several small bright spots where stars are forming. A few foreground stars with small diffraction spikes can be seen in front of the galaxy.]

Links

Pan video: ESO 422-41

Size distribution for unknown asteroids in Hubble asteroid hunter survey

Thu, 18 Apr 2024 16:00:00 +0200

This graph is based on Hubble Space Telescope archival data that were used to identify a largely unseen population of very small asteroids. The asteroids were not the intended targets, but instead photobombed background stars and galaxies in Hubble images. The comprehensive treasure hunt required perusing 37 000 Hubble images spanning 19 years. This was accomplished by using ‘citizen science’ volunteers and artificial intelligence algorithms. The payoff was finding 1701 trails of previously undetected asteroids.

[Image description: This graph plots the size of asteroids versus their abundance, based on a Hubble Space Telescope archival survey that found 1701 mostly previously undetected asteroids lying between the orbits of Mars and Jupiter. The vertical axis lists the number of objects from zero to 70. The horizontal axis lists size, from zero kilometres on the left, to 2 kilometres on the right. The graph slopes up such that the most abundant asteroids detected by Hubble in the survey are 0.5 kilometres across in size.]

Asteroid photobombs Hubble snapshot of Galaxy UGC 12158 (compass image)

Thu, 18 Apr 2024 16:00:00 +0200

This is an annotated NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158, with compass arrows, a scale bar, and colour key for reference. It looks like someone took a white marking pen to it. In reality it is a combination of time exposures of a foreground asteroid moving through Hubble’s field of view, photobombing the observation of the galaxy. Several exposures of the galaxy were taken, which is evidenced by the dashed pattern.

The asteroid appears as a curved trail as a result of parallax: Hubble is not stationary, but orbiting Earth, and this gives the illusion that the faint asteroid is swimming along a curved trajectory. The uncharted asteroid is inside the asteroid belt in our Solar System, and hence is 10 trillion times closer to Hubble than the background galaxy.

Rather than being a nuisance, this type of data is useful to astronomers for doing a census of the asteroid population in our Solar System.

[Image description: Annotated image of barred spiral galaxy UGC 12158 against the black background of space, with compass arrows, a scale bar, and colour key for reference. The galaxy has a pinwheel shape made up of bright blue stars wound around a yellow-white hub of central stars. The galaxy is tilted face-on to our view from Earth. A slightly S-shaped white line across the top is the Hubble image of an asteroid streaking across Hubble’s view. Indicated filters are expressed as: “F475W” in blue, “F606W” in green, and “F814W” in red. At the bottom left corner is a scale bar labelled “60,000 light-years” over “30 arcseconds.” At the bottom right corner, the “E” compass arrow points towards the 2 o’clock position. The “N” compass arrow points towards the 5 o’clock position.]

Asteroid photobombs Hubble snapshot of Galaxy UGC 12158

Thu, 18 Apr 2024 16:00:00 +0200

This NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158 looks like someone took a white marking pen to it. In reality it is a combination of time exposures of a foreground asteroid moving through Hubble’s field of view, photobombing the observation of the galaxy. Several exposures of the galaxy were taken, which is evidenced by the dashed pattern.

Rather than being a nuisance, this type of data is useful to astronomers for doing a census of the asteroid population in our Solar System.

[Image description: This is a Hubble Space Telescope image of the barred spiral galaxy UGC 12158. The majestic galaxy has a pinwheel shape made up of bright blue stars wound around a yellow-white hub of central stars. The hub has a slash of stars across it, called a bar. The galaxy is tilted face-on to our view from Earth. A slightly S-shaped white line across the top is the Hubble image of an asteroid streaking across Hubble’s view. It looks dashed because the image is a combination of several exposures of the asteroid flying by like a race car.]

The eponymous NGC 3783

Mon, 15 Apr 2024 06:00:00 +0200

This image features NGC 3783, a bright barred spiral galaxy about 130 million light-years from Earth, that also lends its name to the eponymous NGC 3783 galaxy group. Like galaxy clusters, galaxy groups are aggregates of gravitationally bound galaxies. Galaxy groups, however, are less massive and contain fewer members than galaxy clusters do: where galaxy clusters can contain hundreds or even thousands of constituent galaxies, galaxy groups do not typically include more than 50. The Milky Way is actually part of a galaxy group, known as the Local Group, which contains two other large galaxies (Andromeda and the Triangulum galaxy), as well as several dozen satellite and dwarf galaxies. The NGC 3783 galaxy group, meanwhile, contains 47 galaxies. It also seems to be at a fairly early stage of its evolution, making it an interesting object of study.

Whilst the focus of this image is the spiral galaxy NGC 3783, the eye is equally drawn to the very bright object in the lower right part of this image. This is the star HD 101274. The perspective in this image makes the star and the galaxy look like close companions, but this is an illusion. HD 101274 lies only about 1530 light-years from Earth, meaning it is about 85 thousand times closer than NGC 3783. This explains how a single star can appear to outshine an entire galaxy!

NGC 3783 is a type-1 Seyfert galaxy, which is a galaxy with a bright central region — so it’s particularly bright itself, as far as galaxies go. In this image it is recorded by Hubble in incredible detail, from its glowing central bar to its narrow, winding arms and the dust threaded through them, thanks to five separate images taken in different wavelengths of light. In fact, the galactic centre is bright enough to Hubble that it exhibits diffraction spikes, normally only seen on stars such as HD 101274.

[Image Description: A spiral galaxy, seen face-on to the viewer. The bright centre of the galaxy is crossed by a glowing bar, and it is surrounded by tightly-wound spiral arms, forming a circular shape with relatively clear edges. Faraway galaxies can be seen around it, along with a few bright stars, on a dark background. One star to the right of the galaxy is very large and extremely bright with long diffraction spikes around it.]

Hidden in a dark cloud

Mon, 08 Apr 2024 06:00:00 +0200

The subject of this week’s Picture of the Week from Hubble is the spiral galaxy IC 4633, located 100 million light-years away from us in the constellation Apus. IC 4633 is a galaxy rich in star-forming activity, as well as hosting an active galactic nucleus at its core. From our point of view, the galaxy is tilted mostly towards us, giving astronomers a fairly good view of its billions of stars.

However, we can’t fully appreciate the features of this galaxy — at least in visible light — because it’s partially concealed by a stretch of dark dust. This dark nebula is part of the Chamaeleon star-forming region, itself located only around 500 light-years from us, in a nearby part of the Milky Way galaxy. The dark clouds in the Chamaeleon region occupy a large area of the southern sky, covering their namesake constellation but also encroaching on nearby constellations, like Apus. The cloud is well-studied for its treasury of young stars, particularly the cloud Cha I, which has been imaged by Hubble and also by the NASA/ESA/CSA James Webb Space Telescope.

The cloud overlapping IC 4633 lies east of the well-known Cha I, II and III, and has been called MW9 or the South Celestial Serpent. A vast, narrow trail of faint gas that snakes over the southern celestial pole, it’s much more subdued-looking than its neighbours. It’s classified as an integrated flux nebula (IFN) — a cloud of gas and dust in the Milky Way galaxy that’s not near to any single star, and is only faintly lit by the total light of all the galaxy’s stars. Hubble has no problem making out the South Celestial Serpent, though this image captures only a tiny part of it. For a showy astronomical object like IC 4633, among the South Celestial Serpent’s coils clearly isn’t a bad place to hide.

[Image Description: A spiral galaxy seen nearly face-on. The disc is made up of many tightly wound spiral arms. They contain small strands of reddish dust, near the centre. On the left side, the disc features glowing patches of star formation. The whole right side, and part of the centre, is obscured by a large cloud of dark grey gas which crosses the image.]

Two’s company

Mon, 01 Apr 2024 06:00:00 +0200

This image features Arp 72, a very selective galaxy group that only includes two interacting galaxies: NGC 5996 (the large spiral galaxy) and NGC 5994 (its smaller companion, in the lower left of the image). Both galaxies lie approximately 160 million light-years from Earth, and their cores are separated from each other by a distance of around 67 thousand light-years. Moreover, the distance between the galaxies at their closest points is even smaller, closer to 40 thousand light-years. Whilst this might still sound vast, in galactic separation terms it is really very cosy! For comparison, the distance between the Milky Way and its nearest independent galactic neighbour Andromeda is around 2.5 million light-years. Alternatively, the distance between the Milky Way and its largest and brightest satellite galaxy, the Large Magellanic Cloud (satellite galaxies are galaxies that are bound in orbit around another galaxy), is about 162 thousand light-years.

Given this, coupled with the fact that NGC 5996 is roughly comparable in size to the Milky Way, it is not surprising that NGC 5996 and NGC 5994 — apparently separated by only 40 thousand light-years or so — are interacting with one another. In fact, the interaction might be what has caused the spiral shape of NGC 5996 to distort and apparently be drawn in the direction of NGC 5994. It also prompted the formation of the very long and faint tail of stars and gas curving away from NGC 5996, up to the top right of the image. This ‘tidal tail’ is a common phenomenon that appears when galaxies get in close together, as can be seen in several Hubble images.

[Image Description: A large spiral galaxy with a smaller neighbouring galaxy. The spiral galaxy is wide and distorted, with colourful dust. Its companion lies close by it at the end of a spiral arm, to the lower left. A long, faint tail of stars reaches up from the right side of the spiral galaxy to the top of the image. Several small, distant galaxies can be seen in the background, as well as one bright star in the foreground.]

Links

Pan video: Arp 72

FS Tau

Mon, 25 Mar 2024 15:00:00 +0100

FS Tau is a multi-star system made up of FS Tau A, the bright star-like object near the middle of the image, and FS Tau B (Haro 6-5B), the bright object to the far right that is partially obscured by a dark, vertical lane of dust. The young objects are surrounded by softly illuminated gas and dust of this stellar nursery. The system is only about 2.8 million years old, very young for a star system. Our Sun, by contrast, is about 4.6 billion years old.

FS Tau B is a newly forming star, or protostar, and is surrounded by a protoplanetary disc, a pancake-shaped collection of dust and gas leftover from the formation of the star that will eventually coalesce into planets. The thick dust lane, seen nearly edge-on, separates what are thought to be the illuminated surfaces of the disc.

FS Tau B is likely in the process of becoming a T Tauri star, a type of young variable star that hasn’t begun nuclear fusion yet but is beginning to evolve into a hydrogen-fueled star similar to our Sun. Protostars shine with the heat energy released as the gas clouds from which they are forming collapse, and from the accretion of material from nearby gas and dust. Variable stars are a class of star whose brightness changes noticeably over time.

FS Tau A is itself a T Tauri binary system, consisting of two stars orbiting each other.

Protostars are known to eject fast-moving, column-like streams of energised material called jets, and FS Tau B provides a striking example of this phenomenon. The protostar is the source of an unusual asymmetric, double-sided jet, visible here in blue. Its asymmetrical structure may be because mass is being expelled from the object at different rates.

FS Tau B is also classified as a Herbig-Haro object. Herbig–Haro objects form when jets of ionised gas ejected by a young star collide with nearby clouds of gas and dust at high speeds, creating bright patches of nebulosity.

FS Tau is part of the Taurus-Auriga region, a collection of dark molecular clouds that are home to numerous newly forming and young stars, roughly 450 light-years away in the constellations of Taurus and Auriga. Hubble has previously observed this region, whose star-forming activity makes it a compelling target for astronomers. Hubble made these observations as part of an investigation of edge-on dust discs around young stellar objects.

[Image description: A bright point of light shines near center-right with diffraction spikes, surrounded by glowing clouds against black space. A blue jet of material extends roughly throughout the center of the image, partially obscured by the clouds.]

No zoom

Mon, 25 Mar 2024 06:00:00 +0100

This image shows a globular cluster known as NGC 1651. Like the object in another recent Picture of the Week, it is located about 162 000 light-years away in the largest and brightest of the Milky Way’s satellite galaxies, the Large Magellanic Cloud (LMC). A notable feature of this image is that the globular cluster almost fills the entire image, even though globular clusters are only about 10 to 300 light-years in diameter (NGC 1651 has a diameter of roughly 120 light-years). In contrast, there are numerous Hubble Pictures of the Week that feature entire galaxies — which can be tens or hundreds of millions of light-years in diameter — that also more or less fill the whole image.

A common misconception is that Hubble and other large telescopes manage to observe wildly differently sized celestial objects by zooming in on them, as one would with a specialised camera here on Earth. However, whilst small telescopes might have the option to zoom in and out to a certain extent, large telescopes do not. Each telescope’s instrument has a fixed ‘field of view’ (the size of the region of sky that it can observe in a single observation). For example, the ultraviolet/visible light channel of Hubble’s Wide Field Camera 3 (WFC3), the channel and instrument that were used to collect the data used in this image, has a field of view roughly one twelfth the diameter of the Moon as seen from Earth. Whenever WFC3 makes an observation, that is the size of the region of sky that it can observe.

The reason that Hubble can observe objects of such wildly different sizes is two-fold. Firstly, the distance to an object will determine how big it appears to be from Earth, so entire galaxies that are relatively far away might take up the same amount of space in the sky as a globular cluster like NGC 1651 that is relatively close by. In fact, there's a distant spiral galaxy lurking in this image, directly left of the cluster — though undoubtedly much larger than this star cluster, it appears small enough here to blend in with foreground stars! Secondly, multiple images spanning different parts of the sky can be mosaiced together to create single images of objects that are too big for Hubble’s field of view. This is a very complex task and is not typically done for Pictures of the Week, but it has been done for some of Hubble’s most iconic images.

[Image Description: A spherical collection of stars, which fills the whole view. The stars merge into a bright, bluish core in the centre, and form a sparse band around that out to the edges of the image. A few stars lie in front of the cluster, with visible diffraction spikes. The background is dark black.]

Brown dwarf (artist’s concept)

Thu, 21 Mar 2024 15:00:00 +0100

This is an artist’s representation of a brown dwarf. This class of object is too large to be a planet (and did not form in the same way), but is too small to be a star because it cannot sustain nuclear fusion, since it is less massive than even the smallest stars. A brown dwarf is likely to be marked by wind-driven horizontal bands of thick clouds that may alternate with relatively cloud-free bands, giving the object a striped appearance. Whirling storm systems as big as terrestrial continents, or even small planets, might exist.

The name ‘brown dwarf’ is actually a misnomer because the object would typically appear red to the naked eye. It is brightest in infrared light. Many brown dwarfs have binary companions. But as they age, the binary system drifts apart and each dwarf goes its separate way, according to a recent Hubble Space Telescope study.

The background stars in this illustration are a science visualisation assembled from the Gaia spacecraft star catalogue. The synthesised stars are accurate in terms of position, brightness, and colour. Because this is not an image of the Milky Way, missing are glowing nebulae and dark dust clouds.

[Image description: This artist’s representation shows a brown dwarf, an object more massive than a planet but smaller than a star. The dwarf is a cherry-red sphere. It has horizontal stripes of various shades of red that are cloud bands. In the dark background there are myriad stars that are inside our Milky Way galaxy.]

The Spider (and not its web)

Mon, 18 Mar 2024 06:00:00 +0100

This gauzy-looking celestial body is UGC 5829, an irregular galaxy that lies about 30 million light-years away. Despite there not being many observations of this relatively faint galaxy, it has the distinction of having a descriptive soubriquet: the Spider Galaxy. Perhaps the distorted galactic arms with their glowing, star-forming tips bring to mind the clawed legs of an arachnid. Somewhat confusingly, there is another, very similarly nicknamed but otherwise entirely distinct, galaxy known as the Spiderweb Galaxy. This galaxy has also been more extensively imaged (notably by Hubble), despite the fact that it lies about 300 times further from Earth than the Spider Galaxy does.

Fortunately, correct galaxy identification does not depend on casual given names. Rather, known galaxies are recorded in at least one catalogue — and often in several — such as the Uppsala General Catalogue of Galaxies, which gives the Spider Galaxy its more formal title of UGC 5829. This same galaxy also has several different designations in various other catalogues: it is, for example, LEDA 31923 in the Lyon-Meudon Extragalactic Database; MCG+06-24-006 in the Morphological Catalogue of Galaxies; and SDSS J104242.78+342657.3 in the Sloan Digital Sky Survey Catalogue. The Spiderweb Galaxy isn’t recorded in all of the same catalogues — each is necessarily limited in scope — but it is included in the LEDA catalogue as LEDA 2826829. It is evidently simpler to not conflate the dull but distinct names LEDA 31923 and LEDA 2826829, than the fun but easily confused Spider and Spiderweb!

[Image Description: An irregular galaxy, consisting of a large central body of dull-coloured stars, with distorted arms around it. The arms are spotted with brightly glowing pink areas where stars are forming, and bluish gas that is brighter than the galactic core. Two large arms flank the left and right of the body, and smaller streams of stars emerge from the top. Other, distant, galaxies can be seen on the edges of the image.]

Jupiter (6 January 2024)

Thu, 14 Mar 2024 15:00:00 +0100

The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in this new image, taken on 6 January 2024, that captures both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.

A pair of storms is visible: a deep red cyclone and a reddish anticyclone, appear to be next to each other at right of centre. They look so red that at first glance, it looks like Jupiter skinned a knee. These storms are rotating in opposite directions, indicating an alternating pattern of high- and low-pressure systems. For the cyclone, there’s an upwelling on the edges with clouds descending in the middle causing a clearing in the atmospheric haze.

The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.

Toward the left edge of the image is the innermost Galilean moon, Io — the most volcanically active body in the Solar System, despite its small size (only slightly larger than Earth's moon). Hubble resolves volcanic outflow deposits on the surface. Hubble's sensitivity to blue and violet wavelengths clearly reveals interesting surface features.

[Image description: Jupiter is banded with stripes of brownish orange, light grey, soft yellow, and shades of cream, with many large storms and small white clouds punctuating the planet. At upper right of centre, a pair of storms appear next to each other: a deep-red, triangle-shaped cyclone and a reddish anticyclone. Toward the far-left edge of this view is Jupiter’s tiny orange-coloured moon Io.]

Jupiter OPAL observations (January 2024)

Thu, 14 Mar 2024 15:00:00 +0100

This 12-panel series of NASA/ESA Hubble Space Telescope images, taken on 5–6 January 2024, presents snapshots of a full rotation of the giant planet Jupiter. The Great Red Spot can be used to measure the planet's real rotation rate of nearly 10 hours. The innermost Galilean satellite, Io, is seen in several frames, along with its shadow crossing over Jupiter's cloud tops. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL).

[Image description: These 12 views of Jupiter were taken by Hubble throughout the planet’s full rotation on 5–6 January 2024. At top centre is the label Hubble Space Telescope Observations of Jupiter. Next to the title are the labels F658N in red, F502N in green, and F395N in blue, which represent the filters and colours used to make these images. The date and time label for each view is centred at the bottom of each image. The Great Red Spot can be used to measure the planet’s real rotation rate of nearly 10 hours. Jupiter’s innermost moon, Io, is seen in several images, along with its shadow, crossing over Jupiter’s cloud tops.]

Hubble’s two new views of Jupiter (January 2024)

Thu, 14 Mar 2024 15:00:00 +0100

The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images, taken on 5–6 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.

[left image] - Big enough to swallow Earth, the classic Great Red Spot stands out prominently in Jupiter's atmosphere. To its lower right, at a more southerly latitude, is a feature sometimes dubbed Red Spot Jr. This anticyclone was the result of storms merging in 1998 and 2000, and it first appeared red in 2006 before returning to a pale beige in subsequent years. This year it is somewhat redder again. The source of the red coloration is unknown but may involve a range of chemical compounds: sulphur, phosphorus or organic material. Staying in their lanes, but moving in opposite directions, Red Spot Jr. passes the Great Red Spot about every two years. Another small red anticyclone appears in the far north.

[right image] - Storm activity also appears in the opposite hemisphere. A pair of storms: a deep red cyclone and a reddish anticyclone, appear to be next to each other at right of centre. They look so red that at first glance, it looks like Jupiter skinned a knee. These storms are rotating in opposite directions, indicating an alternating pattern of high- and low-pressure systems. For the cyclone, there’s an upwelling on the edges with clouds descending in the middle causing a clearing in the atmospheric haze.

The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.

[Image description: A side-by-side image showing both faces of Jupiter on the black background of space. The left image is labelled January 5, 2024. Jupiter is banded with stripes of brownish orange, light grey, soft yellow, and shades of cream, punctuated with many large storms and small white clouds. The Great Red Spot is the most prominent feature in the left bottom third of this view. The right image is labelled January 6, 2024. This opposite side of Jupiter is also banded with stripes of brownish orange, light grey, soft yellow, and shades of cream. At upper right of centre, a pair of storms appear next to each other: a deep-red, triangle-shaped cyclone and a reddish anticyclone. Toward the far-left edge of this view is Jupiter’s tiny orange-coloured moon Io.]