We observe a star that is dstar away. How much extinction would there need to be (i.e., what must 7 be) if we had ignored intervening dust, and concluded that it was actually 2 dstar away? Value: dstar = 913 pc Give your response to two decimal places.

What evidence is there that star formation has occurred recently?

Planetary Nebula Age. Suppose a planetary nebula is 1 pc in radius. If the Doppler shifts in its spectrum show it is expanding at 20 km/s, how old is it? (Note that 1 pc equals 3.1x1013 km, and 1 year equals 3.2x107 seconds, to two significant figures.) Please round your answer to two significant digits. At = years

A) A typical dust grain has a radius of about 0.1 micrometers and a mass of  10-14   grams. Roughly how many dust particles are in a cloud containing 1000 Msun of dusty gas if 1% of the cloud's mass is in the form of dust grains?  B) What surface area would be covered by these grains if you put them side by side? Assume these grains are spherical. Answer in square light-years. C) Estimate the total surface area covered by the cloud assuming it's matter density is like that of a typical molecular cloud, about 10-21 g/cm3 (Hint: first calculate the clouds volume from it's mass and density, then determine its radius using the formula for volume of a sphere) Answer in square light-years.  D) Comparing all above answers, What are the chances (very roughly) that a photon passing through the cloud will hit a dust grain?

How many years? Thank you!

Describe the Nebular Theory. Include A) what it is, B)what happened, and C) at least three lines of evidence to support it.

For the following light curve, which of the answers best illustrates the orientation of the exoplanet and its host star during the dip at Time 3? Light curve Time 1 Time 2 Time 3 Time 4 Choose one: А. O C. D. Intensity B.

There are two parts to this question. I need to know how many times fainter Venus is from a distance of 6 pc and what the apparent magnitude would be as well! Thank you!!