A closer look at the spur, blob, wiggle, and gaps in GD-1
  The GD-1 stream is one of the longest and coldest stellar streams discovered
to date, and one of the best objects for constraining the dark matter
properties of the Milky Way. Using data from {\it Gaia} DR2 we study the proper
motions, distance, morphology and density of the stream to uncover small scale
perturbations. The proper motion cleaned data shows a clear distance gradient
across the stream, ranging from 7 to 12 kpc. However, unlike earlier studies
that found a continuous gradient, we uncover a distance minimum at
$\varphi_{1}\approx$-50 deg, after which the distance increases again. We can
reliably trace the stream between -85$<\varphi_{1}<$15 deg, showing an even
further extent to GD-1 beyond the earlier extension of \citet{Price-Whelan18a}.
We constrain the stream track and density using a Boolean matched filter
approach and find three large under densities and find significant residuals in
the stream track lining up with these gaps. In particular, a gap is visible at
$\varphi_{1}$=-3 deg, surrounded by a clear sinusoidal wiggle. We argue that
this wiggle is due to a perturbation since it has the wrong orientation to come
from a progenitor. We compute a total initial stellar mass of the stream
segment of 1.58$\pm$0.07$\times$10$^{4}$ M$_{\odot}$. With the extended view of
the spur in this work, we argue that the spur may be unrelated to the adjacent
gap in the stream. Finally, we show that an interaction with the Sagittarius
dwarf can create features similar to the spur.
