Galileo Galilei

Galileo was born in Pisa, but later moved with his family to Florence. In 1581, he enrolled in the University of Pisa to study medicine, then switched to mathematics and natural philosophy. He investigated many areas of science, and is perhaps most famous for his discovery of the four largest moons of Jupiter (still called the Galilean moons). Galileo’s observations led him to support the Sun-centered model of the solar system, which at the time was in opposition to the teachings of the Roman Catholic Church. In 1633, he was tried and made to recant this and other ideas. He was sentenced to house arrest, which lasted the rest of his life. During his confinement, he wrote a book summarizing his work on kinematics (the science of movement).

Key works:

1623 The Assayer

1632 Dialogue Concerning the Two Chief World Systems

1638 Discourses and Mathematical Demonstrations Relating to Two New Sciences

Haley’s Comet

Today in Space History —> On this day in 837, Halley’s Comet made its closest approach to earth at a distance of 5.1 million kilometres. Its earliest verifiable mention was 240 BC and it became famous in Europe in 1066 when it was interpreted as an omen before the Battle of Hastings.

Southern Ellipse

AM 0644-741, a ring galaxy in Volans

AM 0644-741 (sometimes called The Southern Ellipse) is a ring galaxy, approximately 300 million light-years away in the direction of the southern constellation Volans. It is receding from us at about 6600 km/sec.

The yellowish off-center nucleus was once the center of a normal spiral galaxy and the overlapping/double ring of brilliant blue star clusters, which currently surrounds the center, is some 150,000 light-year in diameter, making it larger than our Milky Way Galaxy.

Ring galaxies are formed when an intruder galaxy plunges directly through the disk of a target galaxy. In the case of AM 0644-741, the galaxy that pierced through the ring galaxy is out of the image but visible in larger-field images.

The collision creates a shock wave that causes the gas and dust to rush outward, somewhat like ripples in a pond after a large rock has been thrown in. As the shock ring plows outward, gas and dust clouds collide, are compressed and then collapse gravitationally to form an abundance of new stars in a ring around the outside.

The rampant star formation explains why the ring is so blue: it is continuously forming massive, young, hot stars, which are blue in color. Another sign of robust star formation is the pink regions along the ring. These are rarefied clouds of glowing hydrogen gas that is fluorescing as it is bombarded with strong ultraviolet light from the blue stars.

Anyone who lives on planets embedded in the ring would be treated to a view of a brilliant band of blue stars arching across the heavens. The view would be relatively short-lived because theoretical studies indicate that the blue ring will not continue to expand forever. After about 300 million years, it will reach a maximum radius, and then begin to disintegrate.

This image is taken by the Hubble Space Telescope.
Image Credit: NASA, ESA, and The Hubble Heritage Team (AURA/STScI)

Tadpole Nebula

The Star Formation In The Tadpole Nebula:

IC410 is a dusty emission nebula located in the constellation of Auriga at about 12.000 ly from Earth. It is part of a larger star forming region that also contains the Flaming Star Nebula. The gas structures in this picture are lit by the radiation from the open star cluster NGC1893 that lies in the center of the nebula. This star cluster is about 4 million years old, but in astronomical terms it is still very young, with hot, massive stars. At the top-left of the star cluster two more dense structures are visible. These are similar to the famous Pillar of Creation and they are composed of dust and gas leftover from the formation of the star cluster and are very likely to give birth to more stars in the future. As can be seen in the picture, these structures point away from the center of the nebula. This is because of the stellar winds and radiation pressure from the stars in NGC 1893. Due to these structure’s shape, the nebula is also called the Tadpoles Nebula.

La Silla Observatory

Our magnificent Milky Way galaxy is radiant over La Silla Observatory. The ESO 3.6-metre telescope is shown to the right, now home to the world’s foremost extrasolar planet hunter: High Accuracy Radial velocity Planet Searcher (HARPS), a spectrograph with unrivalled precision.

Photo Credit: ESO/B. Tafreshi

InSight Detects Two Quakes

NASA’s InSight lander has detected two strong, clear quakes originating in a location of Mars called Cerberus Fossae—the same place where two strong quakes were seen earlier in the mission. The new quakes have magnitudes of 3.3 and 3.1; the previous quakes were magnitude 3.6 and 3.5. InSight has recorded over 500 quakes to date, but because of their clear signals, these are four of the best quake records for probing the interior of the planet.

Studying marsquakes is one way the InSight science team seeks to develop a better understanding of Mars’ mantle and core. The planet doesn’t have tectonic plates like Earth, but it does have volcanically active regions that can cause rumbles. The March 7 and March 18 quakes add weight to the idea that Cerberus Fossae is a center of seismic activity.

“Over the course of the mission, we’ve seen two different types of marsquakes: one that is more ‘Moon-like’ and the other, more ‘Earth-like,'” said Taichi Kawamura of France’s Institut de Physique du Globe de Paris, which helped provide InSight’s seismometer and distributes its data along with the Swiss research university ETH Zurich. Earthquake waves travel more directly through the planet, while those of moonquakes tend to be very scattered; marsquakes fall somewhere in between. “Interestingly,” Kawamura continued, “all four of these larger quakes, which come from Cerberus Fossae, are ‘Earth-like.'”

The new quakes have something else in common with InSight’s previous top seismic events, which occurred almost a full Martian year (two Earth years) ago: They occurred in the Martian northern summer. Scientists had predicted this would again be an ideal time to listen for quakes because winds would become calmer. The seismometer, called the Seismic Experiment for Interior Structure (SEIS), is sensitive enough that, even while it is covered by a dome-shaped shield to block it from wind and keep it from getting too cold, wind still causes enough vibration to obscure some marsquakes. During the past northern winter season, InSight couldn’t detect any quakes at all.

“It’s wonderful to once again observe marsquakes after a long period of recording wind noise,” said John Clinton, a seismologist who leads InSight’s Marsquake Service at ETH Zurich. “One Martian year on, we are now much faster at characterizing seismic activity on the Red Planet.”

Sources: Phys.org