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AStro - science

To make sense of which parts of the universe is visible, I have tried to construct some simple concepts of our place in the universe.

The view from earth at midnight, is much like light from a lighthouse. The view, shown as a "tube", following earths orbit around the sun. In June the view is of the core of the Milky Way. The core blocks the view of the universe beyond the core.

Understanding the view from earth is a bit of a brain-tease that has confused people on and off for thousands of years. For the purposes of viewing the Universe, we need the darkest possible skies.

Days - Earth spins on its axis, giving rise to our days and nights.

Months - determined by the orbit of the moon around the earth that gives rise to our monthly cycle and the daily tides. The best viewing are found with the darkest skies that occur when at midnight, the moon is on the same side as the sun. The moon appears during the day and is backlite by the sun - a "New Moon".

Earth orbits the sun, giving rise to our year. The Earths spin axis points at the star Polaris and is tilted 23 degrees to the plane earth/sun orbit, giving rise to the seasons. In June with summer in the northern hemisphere occurring when oriented with the spin axis. For the observer, the nights in the northern hemisphere are longest.

The darkest sky occurs at midnight when the observer is on the opposite side of earth to the sun. The simplest reference view is 180 degrees centered on directly overhead. In the spin direction, the view from dark skies after sunset to sunset covers a roughly 270 degree view.

The by month view of the Milky Way at midnight from Austin TX, 35 degrees North. Best views overhead in August and January.

The ecliptic at night is the opposite of the day, overhead in the winter, low in the sky in summer. The ecliptic is fixed relative to Milky Way,

In March, the Milky way is just on the horizon, hence my photo in Marathon in 2021.

The white hemispheres illustrate the 180 degree view from the equator The plane of the earths spin rotation relative to the plane of the orbit around the sun (ecliptic) , affects the view in June and December.

The sketch shows the how the view of the Milky Way works. It starts from the Suns location in the plane of the Milky Way.

The earth-sun orbital plane (ecliptic) is oriented at 63 degrees to the plane of the Milky Way pointing at the galactic center. The north spin axis of the Earth at 23 degrees to the ecliptic, is oriented away from the center of the Milky Way, fixing the seasons so that earth is positioned between the core and sun in June. The overhead view from the equator on earth at midnight is always directly away from the Sun. At midnight in June, the view is of the center of the Milky Way. At midnight in December, the overhead view from earth is directly way from the center of the Milky Way.

The "pictures" of the Milky Way are for an observer at the equator. As the observer moves towards the poles, portions of the core get obscured.

Andromeda and other deep sky objects outside Milky Way are visible in mid-winter.

For the northern deep sky galaxies, June will position the galaxies low in the E-NE sky to give a good alignment with foreground objects. Moon in the SE.

For galaxies just south of the Milky Way, they are low in the NE sky Aug and Sept.

The target galaxies and moon all to scale are shown. The idea is to show all these behind elements of the capitol for scale.

Nebula

This NASA Spitzer Space Telescope image reveals a glowing stellar nursery embedded within the Elephant’s Trunk Nebula, an elongated dark globule within the emission nebula IC 1396 in the constellation of Cepheus. Located at a distance of 2,450 light-years, the globule is a condensation of dense gas that is barely surviving the strong ionizing radiation from a nearby massive star. The globule is being compressed by the surrounding ionized gas. The Spitzer Space Telescope pierces through the obscuration to reveal the birth of new protostars, or embryonic stars, and previously unseen young stars. The infrared image was obtained by Spitzer’s infrared array camera and is a four-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8.0 microns (red). The filamentary appearance of the globule results from the sculpting effects of competing physical processes. The winds from a massive star, located to the right of the image, produce a dense circular rim comprising the ‘head’ of the globule and a swept-back tail of gas. A pair of young stars (LkHa 349 and LkHa 349c) that formed from the dense gas has cleared a spherical cavity within the globule head. While one of these stars is significantly fainter than the other in visible-light images, they are of comparable brightness in the infrared Spitzer image. This implies the presence of a thick and dusty disc around LkHa 349c. Such circumstellar discs are the precursors of planetary systems. They are much thicker in the early stages of stellar formation when the

Rosette Nebula

The cluster and nebula lie at a distance of 5,000 light-years from Earth[5] and measure roughly 130 light years in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation themselves producing the emission nebula we see. The mass of the nebula is estimated to be around 10,000 solar masses.

Chandra X-ray image overlaying an optical image reveals hundreds of young stars (red points inside the boxes).

A survey of the nebula with the Chandra X-ray Observatory has revealed the presence of numerous new-born stars inside optical Rosette Nebula and studded within a dense molecular cloud. Altogether, approximately 2500 young stars lie in this star-forming complex, including the massive O-type stars HD 46223 and HD 46150, which are primarily responsible for blowing the ionized bubble.[6][7] Most of the ongoing star-formation activity is occurring in the dense molecular cloud to the south east of the bubble.[8]

A diffuse X-ray glow is also seen between the stars in the bubble, which has been attributed to a super-hot plasma with temperatures ranging from 1 to 10 million K.[9] This is significantly hotter than the 10,000 K plasmas seen in HII regions, and is likely attributed to the shock-heated winds from the massive O-type stars.