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  • Writer's pictureMatt Russell


This week we talk about CHEOPS and chat with some of the CHANDRA team about 20 years of images and changing our understanding of science.

December 20th the 354th day of the year, one of the saddest days in the calendar, passing away in 1996 – Carl Sagan, American astronomer, astrophysicist, and cosmologist (b. 1934)


The Chandra bunch!!!

BOOK: light from the Void, a stunning collection of photographs from the Chandra X-Ray Observatory's two decades of operation


Kimberly Arcand has been a member of the Chandra X-ray Center since 1998. As the Visualization Lead,

Megan Watzke is the press officer for NASA's Chandra X-ray Observatory.

Grant Tremblay Astrophysicist at the Center for Astrophysics | Harvard & Smithsonian

Here are a couple of the pictures we talked about, txt from APOD

Explanation: A truly enormous collection of thousands of galaxies, the Perseus Cluster - like other large galaxy clusters - is filled with hot, x-ray emitting gas. The x-ray hot gas (not the individual galaxies) appears in the left panel above, a false color image from the Chandra Observatory. The bright central source flanked by two dark cavities is the cluster's supermassive black hole. At right, the panel shows the x-ray image data specially processed to enhance contrasts and reveals a strikingly regular pattern of pressure waves rippling through the hot gas. In other words, sound waves, likely generated by bursts of activity from the black hole, are ringing through the Perseus Galaxy Cluster. Astronomers infer that these previously unknown sound waves are a source of energy which keeps the cluster gas so hot. So what note is the Perseus Cluster playing? Estimates of the distance between the wave peaks and sound speed in the cluster gas suggests the cosmic note is about 57 octaves below B-flat above middle C.

Explanation: The matter in galaxy cluster 1E 0657-56, fondly known as the "bullet cluster", is shown in this composite image. A mere 3.4 billion light-years away, the bullet cluster's individual galaxies are seen in the optical image data, but their total mass adds up to far less than the mass of the cluster's two clouds of hot x-ray emitting gas shown in red. Representing even more mass than the optical galaxies and x-ray gas combined, the blue hues show the distribution of dark matter in the cluster. Otherwise invisible to telescopic views, the dark matter was mapped by observations of gravitational lensing of background galaxies. In a text book example of a shock front, the bullet-shaped cloud of gas at the right was distorted during the titanic collision between two galaxy clusters that created the larger bullet cluster itself. But the dark matter present has not interacted with the cluster gas except by gravity. The clear separation of dark matter and gas clouds is considered direct evidence that dark matter exists.


This week saw the flight of VS23 a Soyuz operating out of French Guiana, Kourou. The primary satellite was COSMO-SkyMed - 1 a 1.9 tonne Italian Earth observation satellite, with synthetic aperture radar (SAR) - for both military and civilian use. The Secondary payload a much smaller and more interesting satellite the 0.3 tonnes Cheops, launched into Sun-synchronous Low Earth circular Orbit altitude 430 miles (700 km)

CHEOPS - CHaracterising ExOPlanet Satellite - will be the first small mission of the ESA Cosmic Vision Programme, dedicated to searching for exoplanetary transits by performing ultrahigh precision photometry on bright stars already known to host planets. And when they say high precision they mean high precision - The instrument that will study these exoplanets is an F/8 12.6” (32cm) Ritchey-Chrétien telescope supplied by the University of Bern, in Switzerland, which is integrated on Spanish Airbus platform, Using it's Teledyne e2v (UK) Limited CCD47-20 Back-Illuminated Frame-Transfer CCD Sensor cooled to 233 K (−40 °C; −40 °F), CHEOPS will measure photometric signals with a precision of 20 ppm in 6 hours of integration time for a 9th magnitude star, in plain English, it can measure the minuscule millionths of a % dimming of a star unbelievably accurately so you can measure the radius of the planet. Ie if the radius was 50% that of the host star it would dim by roughly 25% Earth’s radius is 100 times smaller than the sun so would dim the light by 0.008%, or 80 ppm of light,

The gap in the Data!!!

We have found and catalogued over 4,500 exoplanets! But there is a small problem, we have a giant catalogue, but most of these planets we know very little about, but why? and how does Cheops help? Using the transit method: the minuscule dimming of the star as a planet passes in front you can infer the radius of that object, Using Radial velocity method, how much a star is being pulled about by the orbiting planets using Doppler shifts of light (colour change as the star is being pulled towards or away from us) you can infer the mass of that planet. If you know both the mass and the radius you can start to work out the density of a planet, so tantalising information on the physical nature of the planet can be obtained.

Despite the two amazing space missions that looked at transit searches in CNES/ESA CoRoT and NASA’s Kepler and the past two decades of high-precision radial velocity measurement from the ground the number of exoplanets in the 1 to 30 x Earth earth mass range for which both mass and radius are accurately known, is pretty small. This is because masses cannot be measured accurately enough by the current Doppler methods, as they are simply too faint to allow the required precision in radial velocity to be reached. We have been left with two populations of exoplanets, one for which we know the mass and one for which we know the radius with very little overlap. The goal of CHEOPS is to significantly increase the sample of objects to have both radius and mass measurements so scientists can determine the structure of the planet and also if the planet has an atmosphere! A list of 400-500 targets to look at over the next 3.5 years. All this for Super-Earth planets, Neptune sized down to the mass of Earth with a precision that simply cannot be achieved from the ground, and will be sending this info down via a 1.2 GBit/day downlink, The first data is expected at the beginning of 2020. Guaranteed Time Observing (GTO) Programme: 80% of the science observing time on CHEOPS is dedicated to the CHEOPS, under the responsibility of the CHEOPS Science Team (chaired by Didier Queloz) The majority of the GTO programme involves the characterization of known transiting exoplanets and improvement of known parameters. Part of the GTO programme is to find transits of known exoplanets that were confirmed by other techniques, such as radial-velocity, but not by the transit-method. Another part of the GTO programme includes exploration of multi-systems and search of additional planets in those systems, for example using the transit-timing-variation The other 20% of the science observing time on CHEOPS is made available to the scientific community in the form of an ESA-run Guest Observers' (GO) Programme. Researchers can submit proposals for observations with CHEOPS through an annual Announcements of Opportunity (AO) Program. The approved AO-1 projects include observations of the hot Jupiters HD 17156 b, Kelt-22A b,[27] warm Jupiter K2-139b,[28] multi-systems GJ 9827, K2-138, the exoplanet DS Tuc Ab,[29] 55 Cancri e (likely GTO), other exoplanet science-related observations, such as planets around rapidly-rotating stars, planet material around white dwarfs and searching for transiting exocomets around 5 Vulpeculae More to come. Also as the bigger telescopes come online and we can measure these doppler shifts more accurately we will be able to add the Cheops data!!! Hubble Space Telescope and MOST (Canadian very small telescope in space) have also found and confirmed a few planets. The infrared Spitzer Space Telescope has been used to detect transits of extrasolar planets, as well as occultations of the planets by their host star and phase curves The Gaia mission, is using astrometry, measuring a star's position in the sky, and observing how that position changes over time, to determine the true masses of 1000 nearby exoplanets NASA’s TESS, launched in 2018, ESA’s PLATO will launch in 2026 both will also use the transit method. James Webb Space Telescope (JWST) will analyse the atmospheres of the planets that are turned up by all these. “use a small telescope 'to identify', and then a bigger telescope 'to understand' - and that's exactly the kind of process we plan to do," said 2019 Physics Nobel laureate Prof Didier Queloz. Told the BBC To reinforce that point from last week that ESA has to develop and invent technology for every mission “When we wanted to test this in the lab we didn't find a single light source in the world that was stable to this precision to allow us to test our telescope - so we had to build one." Professor Dr Willy Benz an astrophysicist and director of the Physics Institute at the University of Bern. He heads the ESA CHEOPS mission.

The CHEOPS mission is a partnership between Switzerland and ESA's Science Programme, with important contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom.

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