Category Archives: ESA

Stellar Bubble

ESA: This turbulent celestial palette of purple and yellow shows a bubble of gas named NGC 3199, blown by a star known as WR18 (Wolf-Rayet 18).

Wolf-Rayet stars are massive, powerful, and energetic stars that are just about reaching the end of their lives. They flood their surroundings with thick, intense, fast-moving winds that push and sweep at the material found there, carving out weird and wonderful shapes as they do so. These winds can create strong shockwaves when they collide with the comparatively cool interstellar medium, causing them to heat up anything in their vicinity. This process can heat material to such high temperatures that it is capable of emitting X-rays, a type of radiation emitted only by highly energetic phenomena in the Universe.

This is what has happened in the case of NGC 3199. Although this kind of scenario has been seen before, it is still relatively rare; only three other Wolf-Rayet bubbles have been seen to emit X-rays (NGC 2359, NGC 6888, and S308). WR18 is thought to be a star with especially powerful winds; once it has run out of material to fuel these substantial winds it will explode violently as a supernova, creating a final breath-taking blast as it ends its stellar life.

This image was taken by the European Photon Imaging Camera (EPIC) on ESA’s XMM-Newton X-ray space observatory, and marks different patches of gas in different colours. The incredibly hot, diffuse, X-ray-emitting gas within the Wolf-Rayet bubble is shown in blue, while a bright arc that is visible in the optical part of the spectrum is traced out in shades of yellow-green (oxygen emission) and red (sulphur emission).

This blue and yellow-green component forms an optical nebula – a glowing cloud of dust and ionised gases – that stretches out towards the western end of the X-ray bubble (in this image, North is to the upper left). This lopsided arc caused astronomers to previously identify WR18 as a so-called runaway star moving far faster than expected in relation to its surroundings, but more recent studies have shown that the observed X-ray emission does not support this idea. Instead, the shape of NGC 3199 is thought to be due to variations in the chemistry of the bubble’s surroundings, and the initial configuration of the interstellar medium around WR18.

Image: SA/XMM-Newton; J. Toalá; D.Goldman


Stellar Nursery

The Herschel Observatory is still responsible for great science even after the four or five-years or so since the end of the mission.

ESA — Stellar nurseries are cloudy and dusty places that shine brightly in infrared light. The G305 star-forming complex is no exception. It features a number of bright, intricate gas clouds heated by infant stars in their midst. In this spectacular image by ESA’s Herschel space observatory, these star-forming hotspots stand out in a blue tone that contrasts with the red-brownish colour of cooler regions.

While there are several star-formation sites dotted throughout this scene, the most striking ones surround the dark, heart-shaped area in the top right of the image. Hidden at the centre of the dark region lie the massive star WR48a and its two neighbours, stellar clusters Danks 1 and 2. All three play an important role in triggering the formation of new stars, even if they themselves are relatively young objects no older than a few million years (for comparison, the Sun is around 4.6 billion years old).

Strong winds and radiation from WR48a and the high-mass stars in the two clusters have pushed away the gas remnants from the cloud where they originated. The swept-away gas, gathered together at the edge of the heart-shaped bubble, is now forming new stars.

Using Herschel, astronomers have identified 16 sites where high-mass stars are forming in this stellar nursery. The region is one of the brightest and most plentiful star-forming complexes in the Milky Way, and an ideal ground to observe and study massive stars at different stages of formation and evolution.

The G305 complex is about 12 000 light-years away and gets its name from its location at around 305º longitude in the plane of our Galaxy. In the night sky, it appears near the Coalsack Nebula, a large interstellar cloud of dust visible to the naked eye and located in the constellation of Crux, the Southern Cross. A very prominent dark nebula, Coalsack shows up in the southern skies as a black patch against the bright, starry backdrop of the Milky Way.

This image, obtained as part of Hi-GAL – the Herschel infrared Galactic Plane Survey, combines observations at three different wavelengths: 70 microns (blue), 160 microns (green) and 250 microns (red).

Launched in 2009, Herschel operated for four years observing at far infrared and submillimetre wavelengths. This spectral range allowed it to observe the glow of dust in gas clouds where stars are born to investigate this process and observe their early evolution.

Image: ESA/Herschel/PACS, SPIRE/Hi-GAL Project. Acknowledgement: UNIMAP / L. Piazzo, La Sapienza – Università di Roma; E. Schisano / G. Li Causi, IAPS/INAF, Italy

The Next Mission for Alexander Gerst

Alexander Gerst will join US astronaut Serena Auñón-Chancellor and Russian cosmonaut Sergei Prokopyev for a trip to the International Space Station from the Baikonur cosmodrome, Kazakhstan in the Soyuz MS-09. Gerst will take command of the space station.

Rotation of the LMC

Wow, what a sight! One day I hope to see the Large Magellanic Cloud, someday perhaps I can do this when I take my “bucket list” ride on The Ghan.


Last week the much-awaited second slew of data from ESA’s Gaia mission was released, providing information on a phenomenal 1.7 billion stars – the richest star catalogue to date.

To put that vast number into context, if you were to count ‘only’ to one billion at a rate of one count per second, it would take more than 30 years. The new data will surely keep astronomers busy for even longer.

The dataset has already revealed fine details about the make-up of the Milky Way’s stellar population and about how stars move, essential information for investigating the formation and evolution of our home Galaxy.

The treasure trove of data also includes information about stars beyond our own Galaxy. One example is illustrated in this image, which focuses on one of the nearest galaxies to our Milky Way, the Large Magellanic Cloud, or LMC.

This image combines the total density of stars detected by Gaia in each pixel with information about the proper motion of stars – their velocity across the sky – which is represented as the texture of the image, giving it a fingerprint-like appearance.

Measuring the proper motion of several million stars in the LMC, astronomers were able to see an imprint of the stars rotating clockwise around the centre of the galaxy. The impression of motion is evoked by the swirling nature of the line texture.

Astronomers are interested to derive the orbits of globular clusters – ancient systems of stars bound together by gravity and found in the halo of the Milky Way – and dwarf galaxies that revolve around the Milky Way. This will provide all-important information to study the past evolution of our Galaxy and its environment.

A similar view based on the total amount of radiation detected by Gaia and colour information about the stars is available here, and an animated view of the rotation of stars within the Large Magellanic Cloud is available here.

Read more about Gaia’s latest data release here.

Acknowledgement: Gaia Data Processing and Analysis Consortium (DPAC); A. Moitinho / A. F. Silva / M. Barros / C. Barata, University of Lisbon, Portugal; H. Savietto, Fork Research, Portugal; P. McMillan, Lund Observatory, Sweden

Image: ESA/Gaia/DPAC

Gaia’s Second Data Release

Based on observations between July 2014 to May 2016, the second release helped produce a catalog of over 500,000,000 start! The catalog includes the most accurate information yet on the positions, brightness, distance, motion, colour and temperature of stars in the Milky Way as well as information on asteroids and quasars.

Sentinel 3B Launching Today

Launching later today (if all goes well of course) from the Plesetsk Cosmodrome in Russia is ESA’s Sentinel 3B. Coverage begins at 17:30 UT / 14:30 ET.

ESA’s caption: The Copernicus Sentinel-3B rocket at the top of the launch tower. The Copernicus Sentinel-3B satellite is scheduled for liftoff on 25 April 2018 from the Plesetsk cosmodrome in northern Russia. Its identical twin, Sentinel-3A, has been in orbit since February 2016. The two-satellite constellation offers optimum global coverage and data delivery for Europe’s Copernicus environment programme.

Image: ESA–S. Corvaja

Waiting For Gaia

Every now and then you will read my lamenting how we need better distance measurements. You might think we know the distances to distant stars, after all we reference distances. The trouble is those measures are only accurate in the broadest sense – we really do need more accuracy.

Gaia aims to change all that! ESA just posted this excellent overview of the Gaia mission.

MACS j1149.5+223

Beautiful image of a huge galaxy cluster with the name of MACS j1149.5+223. The galaxy cluster is only 5,000-million light-years away!

What’s more, this image contains a star which is “visible” because of a gravitational lens effect, it is actually much more distant. You’ll not see it in the image above but there is a link in ESA’s description below that does show it.

Before we get to the description, I was must musing about who is going to be the one(s) that come up with a way to reconstruct the lensed images? Oh it’s coming all right, has to be, we have too much great talent out there. It will be Nobel Prize time.

The original caption from ESA:

  • This image shows the huge galaxy cluster MACS J1149.5+223, whose light took over 5 billion years to reach us.The huge mass of the cluster is bending the light from more distant objects. The light from these objects has been magnified and distorted due to gravitational lensing. The same effect is creating multiple images of the same distant objects.

    Astronomers using the NASA/ESA Hubble Space Telescope have found the most distant star ever discovered. The hot blue star existed only 4.4 billion years after the Big Bang. This discovery provides new insight into the formation and evolution of stars in the early Universe, the constituents of galaxy clusters and also on the nature of dark matter.

    Go to Hubble uses cosmic lens to discover most distant star ever observed [heic1525] to learn more.

    Image: NASA, ESA, S. Rodney (John Hopkins University, USA) and the FrontierSN team; T. Treu (University of California Los Angeles, USA), P. Kelly (University of California Berkeley, USA) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

The CAT in Orion

The title from ESA for this is: “THE CAT IN ORION – OR WAS IT A FOX?” I was going it’s a FOX!! Has to be.

Then I read the caption ESA included with the the image – it’s a CAT. Good eyes but we don’t know who was the first to spot the cat from the originators at ESA, Gaia or DPAC.

What’s really amazing is this is the work of Gaia.

The caption: What is the first creature that comes to mind when you look at the dark cloud in this image? Perhaps a dark kitten with a vivid white nose, front paws stretching towards the right of the frame and tail up towards the left? Or perhaps a fox, running with its mouth open and looking ahead, its vigilant eyes pointing to the right?

In fact, this animal-themed shape belongs to a dark nebula, a dense cloud of gas and dust in the constellation of Orion, the Hunter, with the cat’s nose (or fox’s eye) corresponding to the Orion Nebula Cluster, a star cluster near the famous Orion Nebula, M42. The image is based on data from the first release of ESA’s Gaia satellite, and shows the density of stars observed while scanning that region of the sky.

While this particular nebula is not visible to the naked eye, similar clouds can be seen against the bright background of the Milky Way from dark locations in the southern hemisphere. Finding shapes in these dark nebulas is part of the astronomical tradition of various cultures, from South America to Australia, that include ‘dark cloud constellations’ resembling a variety of creatures in their firmaments.

Launched in 2013, Gaia has been charting more than a billion stars to unprecedented accuracy. This information is extremely valuable to astronomers who are studying the distribution of stars across our Galaxy.

Even in the dark patches where fewer stars are observed, Gaia’s meticulous census provides important information to study the interstellar material that blocks starlight. It is in these dark clouds of gas and dust that new generations of stars come to life.

The first data release from Gaia, published in 2016, contained the position on the sky of more than a billion stars, as well as the distance and motions of about two million stars. Astronomers worldwide are now looking forward to the next data release, planned for 25 April, which will include the distance and motions for the full sample of stars, greatly extending the reach of the previous survey.

So far, Gaia data have been used to study only the most nearby regions of star formation, within several hundred light-years of us. With the new data, it will be possible to investigate in great detail regions that are much farther away, like the Orion star-forming complex, located some 1500 light-years from us, and to estimate the 3D distribution not only of stars but also of the dusty dark clouds where stars are born.

More on Gaia’s view of dark interstellar clouds